1. Field of the Invention
The present invention relates to a microphone unit for stereophonic recording in which a pair of right and left unidirectional microphones are arranged so that respective recording axes of the pair of microphones are substantially intersected, and more particularly, to a microphone unit for stereophonic recording capable of adjusting a intersected angle of the recording axes in accordance with circumstances without deteriorating directivity and sound quality of the microphone.
2. Description of the Related Art
Several methods are in practical use as a stereophonic recording method, and an XY type is generally used because of being most general and reliable method. The XY type is a method of collecting sound by arranging a pair of right and left unidirectional microphones in an inverted V-shape so that respective recording axes of the pair of microphones are intersected. The sound collecting axis is a virtual axis line perpendicularly extending from a surface of a diaphragm for sensing sound, and agrees with a direction of the highest sensitivity of the microphone. It is possible to obtain a desired sound image by adjusting the intersecting angle of the sound collecting axes of the one pair of microphones. However, an optimal angle and microphone setting positions are varied by receiving influences caused by various conditions such as an acoustic characteristic of a sound collecting place, and hence success or failure in stereophonic recording largely depends on an experience and a technical skill of a person who sets the microphones. For that reason, there is proposed a microphone unit including two microphones each are arranged in advance so as to form an inverted V-shape without disposing two independent microphones, respectively, in which the intersecting angle of the sound collecting axes may be adjusted.
Japanese Utility Model Laid-open No. Sho. 51-84427 discloses an XY type microphone. This has such a structure that microphone elements are each mounted onto gears having the same diameter mating with each other, and a pinion is allowed to mate with one of the gears so that an opening angle of the microphone elements may be adjusted by rotating the pinion.
In the microphone unit disclosed in Japanese Utility Model Laid-open No. Sho. 51-84427, a structure of the moving part becomes complicate, and further, in order to retain the strength, respective components must be strong and big. The unidirectional microphone largely suffers influences of an area of a rear opening and a shape of an obstacle in the rear opening direction, and hence the directivity and sound quality degrade in the above-mentioned structure.
Japanese Patent Application Laid-open No. 2007-43510 discloses such a structure that right and left microphones are mounted onto the moving bases movable along a rail of a semicircular shape, thereby being capable of arbitrary adjusting the directions of the microphones.
In the microphone unit disclosed in Japanese Patent Application Laid-open No. 2007-43510, too, a scale of the structure for moving the moving bases is large, thereby causing problems of the strength and weight thereof, and in addition, it is difficult to adjust the positions of the microphones because the moving bases may be freely moved within a certain range. Further, because routing distances of signal lines connected to the microphones become larger, there was liable to cause a breakage of the lines.